So?
I know a month to month tenant must be given 15 day notice for termination (I said so in my first response), but I'm not sure that applies to changes in the rental terms. Do you have a cite for that, as well as the abandonment time frame?
There is also the issue of how one defines absent. A person can go on vacation for two weeks. That's half the monthly rental period. Are you going to take over the property in those circumstances? Does the statute say a MINIMUM of 1/2?
I stand by what I said, that if you find that her belongings have been removed and you can provide proof of that, especially since you have given her a pay or quit notice, you can change the locks. Are you ready to go into court for the eviction order tomorrow morning?